1. Field of the Invention
The present invention relates to an X-ray detector and, more particularly, to an X-ray detector with improved thin film transistor layout in which the capacitance value between the data line and the gate line can be reduced by decreasing the overlapping area between the data line and the gate line.
2. Description of Related Art
An X-ray detector is a device configured to detect X-ray digital image and can be applied in digital radiography. Compared to screen-film radiography, digital radiography has various advantages, such as better image quality, simple operation process and direct digital image capture.
FIGS. 1 and 2 show top views of conventional InGaZnO thin film transistors (IGZO TFTs) fabricated by an etching stop process. The thin film transistor shown in FIG. 1 includes a gate electrode 11, a source electrode 12, a drain electrode 13 and an IGZO layer 16. The source electrode 12 and the drain electrode 13 are respectively connected to the IGZO layer 16 through conductive via holes 14, 15. Further, the IGZO layer 16 extends beyond the gate electrode 11 and the conductive via holes 14, 15. Accordingly, in the thin film transistor illustrated in FIG. 1, the overlapping regions of the gate line and the data line contain the areas of both the conductive via holes 14, 15. As for another thin film transistor of FIG. 2 similar to that illustrated in FIG. 1, the width of the IGZO layer 16 is smaller than the width of the gate 11, and the conductive via holes 14, 15 are formed within the peripheral edges of the IGZO layer 16. Likewise, in the thin film transistor of FIG. 2, the overlapping regions of the gate line and the data line contain the areas of both the conductive via holes 14, 15.
For the above conventional pixel layout, the large overlapping areas between the data line and the gate line can cause high capacitance value therebetween and thus induce the increase of noise in signal reading and degradation of image quality.
Accordingly, for the InGaZnO (IGZO) thin film transistor in the X-ray detector, the reduction of capacitance value by decreasing the overlapping areas between data line and gate line is a key point to enhance the image quality of the X-ray detector.